Syntax
resource
stream_filter_append ( resource stream, string filtername [, int read_write [, mixed params]] )
Adds filtername to the list of filters
attached to stream. This filter will be
added with the specified params
to the end of the list and
will therefore be called last during stream operations. To
add a filter to the beginning of the list, use
stream_filter_prepend().
By default, stream_filter_append() will
attach the filter to the read filter chain
if the file was opened for reading (i.e. File Mode:
r, and/or +). The filter
will also be attached to the write filter chain
if the file was opened for writing (i.e. File Mode:
w, a, and/or +).
STREAM_FILTER_READ,
STREAM_FILTER_WRITE, and/or
STREAM_FILTER_ALL can also be passed to the
read_write parameter to override this behavior.
As of PHP 5.1.0, this function returns a resource which
can be used to refer to this filter instance during a call
to stream_filter_remove().
Prior to PHP 5.1.0, this function returns TRUE on success
or FALSE on failure.
Example 1. Controlling where filters are applied
<?php
/* Open a test file for reading and writing */
$fp = fopen("test.txt", "rw");
/* Apply the ROT13 filter to the
* write filter chain, but not the
* read filter chain */
stream_filter_append($fp, "string.rot13", STREAM_FILTER_WRITE);
/* Write a simple string to the file
* it will be ROT13 transformed on the
* way out */
fwrite($fp, "This is a test\n");
/* Back up to the beginning of the file */
rewind($fp);
/* Read the contents of the file back out.
* Had the filter been applied to the
* read filter chain as well, we would see
* the text ROT13ed back to its original state */
fpassthru($fp);
fclose($fp);
/* Expected Output
---------------
Guvf vf n grfg
*/
?>
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When using custom (user) filters:
stream_filter_register() must be called first
in order to register the desired user filter to filtername.
Note:
Stream data is read from resources (both local and remote) in chunks,
with any unconsumed data kept in internal buffers. When a new
filter is appended to a stream, data in the internal buffers is processed through
the new filter at that time. This differs from the behavior of
stream_filter_prepend().
See also
stream_filter_register(),
stream_filter_prepend(), and
stream_get_filters().